Developing for Switch is currently invitation only. Practically speaking, without publisher to provide dev kit you probably won't get one, yet. Even more experienced developers have reportedly trouble to acquire one.

3) And final option, wait it out. No one knows how long it will be invitation only, but if your game is still in early phase, this might be most viable option. In mean time, you can improve your game and do hardware specific matters later. Of course, if your game is practically done, you might try second option.